Spreader systems for hauling and spreading granular materials are well-known. For instance and without being limitative, these spreader systems are used for spreading salt and sand on roads in order to melt snow and ice during winter. Trucks for spreading sand and salt usually have a frame or haul a trailer including one or several bins or hoppers mounted thereon. The particular materials are conveyed outwardly of the bins or hoppers through one or several conveyors. The discharge chute of the spreader is typically positioned at the rear or the front of the respective bin.
Due to variable road or ground conditions, the ratio of granular materials spread must often be varied along the vehicle run. There is thus a need for a spreader assembly which can convey and spread more than one granular material and which can provide variable mixtures of granular materials.